FIG. 1 shows the network elements in an exemplary Mobile wireless network, for example, a 3G/UMTS network. The wireless network includes a Radio Access Network (RAN) and a Core Network (CN).
The GGSN (Gateway GPRS Service Node) connects the mobile wireless network to the IP Core Network. The Gateway GPRS Support Node (GGSN) is a main component of the GPRS (General Packet Radio Service) network. The GGSN is responsible for compatibility between the GPRS network and external packet switched networks, such as the Internet and X.25 networks.
When viewed from an external network, the GGSN appears as a router to a sub-network, because the GGSN hides the GPRS infrastructure from the external network. When the GGSN receives data addressed to a specific user, it checks if the user is active. If it is, the GGSN forwards the data to the SGSN serving the mobile user. However if the mobile user is inactive, the data are discarded, or a paging procedure is initiated to locate and notify the mobile device. For data originated within the GPRS network, the GGSN routes these mobile-originated packets to the correct external network.
The GGSN converts the GPRS packets coming from the SGSN into the appropriate packet data protocol (PDP) format (e.g., IP or X.25) and sends them out on the corresponding packet data network. For incoming packets, the PDP addresses are converted to the GSM (Global System for Mobile communications) address of the destination user. The readdressed packets are then sent to the responsible SGSN. In order to accomplish this function, the GGSN stores the current SGSN address of the user and its associated profile in its location register. The GGSN is responsible for IP address assignment and is the default router for the connected user equipment (UE). The GGSN also performs authentication functions.
A Serving GPRS Support Node (SGSN) is responsible for the delivery of data packets from and to the mobile stations within its geographical service area. Its tasks include packet routing and transfer, mobility management (attach/detach and location management), logical link management, and authentication and charging functions. The location register of the SGSN stores location information and user profiles of all GPRS users registered with this SGSN.
The Radio Network Controller (or RNC) is a governing element in the radio access network and is responsible for controlling the Node Bs that are connected to it. The RNC carries out radio resource management, some of the mobility management functions and is the point where encryption is done before user data is sent to and from the mobile. The RNC connects to the SGSN (Serving GPRS Support Node) in the Packet Switched Core Network.
Node B is a term used to denote the base transceiver station (BTS) in the UMTS/3GPP Architecture. As in all cellular systems, such as GSM, Node B (or BTS) contains radio frequency transmitter(s) and the receiver(s) used to communicate directly with the user equipment, which move freely around it.
The UE comprises all user equipment, including handsets, smart phones and computing equipment.
Regardless of the underlying physical transport medium, most Internet applications use Client-Server Architectures, where the Client and Server are two different applications (Layer 7) in two different devices that communicate through the Internet using TCP/IP protocols. The sequence of operations followed for a typical transaction is shown in FIG. 2.
While this example shows the accessing of a website, the sequence shown is applicable to many other applications as well. For example, when accessing an Internet site, such as yellow pages on www.yahoo.com, the user first starts the client application, as shown in step 1. In this example, the client application would preferably be a web-browser. The user then enters the domain name of the site he intends to access. The client device generates a DNS Query to the default DNS server, as shown in step 2, which then translates the domain name to an IP Address. In step 3, the DNS server returns the response that contains one or more IP addresses that correspond to the name of the intended site. The Client side, in step 4, then generates a TCP Connect (TCP/SYN) request to connect to Server's port number (for example HTTP Port) at the IP address contained in the DNS Response. The application server then returns an acknowledgement (TCP/SYN-ACK), as shown in step 5. The client responds with a TCP/ACK in step 6 and establishes a TCP connection. The client application (i.e. the browser) then sends an HTTP Request to the server, as shown in step 7. In step 9, the server returns an HTTP Response, which includes the Home Page of www.yahoo.com, which contains the link for yellow pages. The user then selects the yellow-pages link. Multiple TCP packets may be exchanged, depending on the size of the page being returned.
In the above sequence, there is a minimum of 3 Roundtrips for receiving the top page of the site, if the HTTP Response is contained in one TCP packet and many more TCP packets if the page is larger. Even if the web page content is contained in single TCP Packet (http-response), before the client-application sees any web-page content, a minimum of 3 round trips elapse. On marginal links, such as in wireless mobile environment, the “Over the Air Bandwidth” (OTA BW) and the round trip times could vary significantly. For example in 3G networks, the round trip time could vary from 100 to 200 milliseconds in good conditions, and much larger (order of seconds) in poor wireless conditions. Thus the delay that user would see before the first page is displayed could be 300 to 600 milliseconds in best conditions.
Because of the long and unpredictable delays associated with wireless networks, especially 3G networks, it would be beneficial if there were a system and method that could reduce the number of required roundtrips between the user and the remote servers.